1. Field of the Invention
The present invention relates generally to lever locks and more particularly, the present invention relates to detents for use with such mechanisms.
2. Description of the Prior Art
Lever locks have been used for some time in a wide variety of applications and situations to lock and secure doors, gates, safety deposit boxes, and the like. Lever locks typically comprise a sliding bolt mechanism. When the bolt is extended outwardly from the case in which it is housed, it typically engages into a hole or mortise in a doorjamb or other fixed member. The bolt is thrown from side to side by way of a portion of an inserted key. As the key turns, the bit end of the key usually contacts the bolt and causes it to slide from side to side as the key is turned.
The lever lock incorporates a plurality of swinging detainers, i.e., a plurality of plate-like levers which swing up and down, or side to side, typically under the force of a spring which biases the levers into a locking position. The key is specifically designed to move or raise these different levers to unique but varying positions or heights such that when the levers are in a particular combination or configuration of heights, a detent is able move due to an external force such as gravity or more typically by a spring force into a specific position. Once in that specific position the detent releases the bolt mechanism allowing it to freely slide into locking or unlocking engagement with the mortise. Typically levers include openings or recesses known as xe2x80x9cgatesxe2x80x9d which are aligned so that a portion of the detent actually slides into the gates of the levers to free the movement of the bolt. The portion of the detent that slides into the gates is known as a fence.
Other lever locks do not use a detent, but instead have the fence connected to the bolt itself. Once the levers are properly aligned, the fence is free to move, thus allowing movement of the bolt.
Three common methods used to defeat lever locks include picking, impressioning and fence breaking. All these methods rely on the ability of the attacker to control the amount of pressure the fence exerts against the levers. The pressure is usually caused using a pick wherein pressure applied to the pick is transferred to pressure of the fence against the levers. As an example, the pressure may be exerted on the fence through the keyhole using a special pick tool that turns the cam, which in turn exerts pressure on the bolt which transfers pressure to the detent, and hence, the fence.
In picking, the pressure of the fence against the levers holds the levers in position while other levers are individually raised to their respective xe2x80x9cunlockedxe2x80x9d position, i.e., a position where all lever gates are properly aligned to allow the fence to move. In impressioning, a large pressure causes levers that are not at a gate to leave a mark on the key being cut. In fence breaking, a substantial pressure is exerted on the bolt, typically using a crowbar or similar tool, causing the fence to actually break thus allowing the lock to open.
Previously, locks have been constructed that were intended to be pick or tamper resistant. For example, locks have been designed to incorporate false gates, jagged-edged levers/fences, detector levers, a spring to compress the stack of levers, a tail on a monitor lever, among others in an attempt to make the above described tamper techniques more difficult. Yet in every design, the attacker still has control over the amount of pressure exerted by the fence against the levers. Hence, while the above methods of attack are made more difficult by these improvements, they are still possible.
For example, in one prior-art lock, a xe2x80x9cdetector leverxe2x80x9d is used to resist tampering. In such a lock, the detector lever is designed to be xe2x80x9ccaughtxe2x80x9d by a spring if it is raised too high. This prevents any further tampering with the lock, as the lock will not open until the detector lever is xe2x80x9creleased.xe2x80x9d Unfortunately however, this does not completely prevent picking of the lock by the usual method, instead it only interrupts the picking process when a lever is raised too high.
In another prior-art lock, the tail on a xe2x80x9cmonitor leverxe2x80x9d is used to foil would-be attackers. In this case, the tail of the monitor lever covers a portion of the keyhole when the lever is raised which makes it difficult to insert the lock picking tools. The tail however, does not directly affect the lock picking process. Similarly, in yet other lock designs, such as locks that use false gates and jagged edges, the features make it difficult to keep the levers in alignment, but do not completely avert picking and do not affect impressioning or fence breaking.
It is with respect to these and other considerations that the present invention has been made.
The present invention relates to a lever lock apparatus having a detent which removes or limits an attacker""s ability to control the amount of force exerted by a fence against the levers. More specifically, when a force is applied to the bolt, the fence of the present invention is forced away from the levers. In essence, the present invention relates to a lever lock apparatus having a detent that performs differently when the lock is being tampered with than when the lock is operated using the correct key. This dual-acting detent swings toward the levers when using the correct key thus allowing the lock to open. However, when an attempt is made to defeat the lock, the detent swings away from the levers preventing the lock from opening and hindering the attempts to defeat the lock.
An aspect of the present invention relates to the directional forces applied to a detent causing both movement to open the lock and movement to prevent the lock from being attacked.
In accordance with other preferred aspects, the present invention relates to lever-lock levers that have frictional components that are much greater than the friction of the fence against the lever end. In order to achieve higher frictional components, i.e., those components other than the fence/lever friction component, the plate faces are roughed or the spring constants can be adjusted to increase the lever frictional components. Additionally, the fence/lever frictional component may be lowered using polished surfaces, rounded edges, lubrication or a reduced spring-biasing force. In preferred embodiments, the amount of possible force exerted by the fence on the levers is insufficient for impressioning and fence breaking.
The invention may be embodied in a key actuated lever lock housed in a case adapted to be mounted in or on a door, gate or the like. Alternatively, the invention may be incorporated into a padlock. The lock includes a bolt housed in the case and adapted to be thrown between a locking position and an unlock position by a thrower mechanism. The bolt has a bolt head adapted for locking engagement in a mortise and a bolt tail plate extending from the bolt head. The tail plate has a bottom edge and defines a notch extending into the plate and opening into the bottom edge. The notch defines opposed talons integral with the tail plate. A recessed area is formed in the tail plate above the talons, and is bounded by internal edges including a recessed bottom edge. The plate further defines a pair of spaced notches opening into the recessed bottom edge that are separated by an upwardly projecting dovetail boss having downwardly and inwardly sloping side edges. An L-shaped detent is pivotally mounted on a detent pivot in the case and defines an arm having a cam rider formed thereon at the lower end thereof. A detent cam is rotatably mounted in the case. A spring biases the detent to hold the cam rider against the detent cam. The detent further defines an elongated laterally extending tail having an upper edge, with a trapezoidal stump integral with the laterally extending detent tail and extending laterally from the upper edge of the tail and defining opposed downwardly and outwardly sloping surfaces.
The stump is adapted to be selectively received in one of the spaced notches, with a sloping edge of the stump in interference engagement with a corresponding sloping edge of the boss.
A key actuated swinging tumbler thrower mechanism is provided for rotating the detent cam to release the detent for spring biased pivoting movement about the detent pivot to release the stump from engagement with the boss and for engaging the talons to throw the bolt when the proper key is used. When the proper key is not used, and a force is applied to the bolt in the unlock direction, the shape of the boss acts on the stump to exert a force on the detent tail urging the detent arm away from the cam and levers thereby thwarting efforts to unlock the lock without a key.